Here is just a little background information that I have found on Challenge Based Learning:

Challenge Based Learning is collaborative and hands-on, asking students to work with other students, their teachers, and experts in their communities and around the world to develop deeper knowledge of the subjects students are studying, accept and solve challenges, take action, share their experience, and enter into a global discussion about important issues.

Challenge Based Learning follows a workflow that mirrors the 21st century workplace. Students are given enough space to be creative and self-directed and at the same time are provided with support, boundaries, and checkpoints to avoid frustration. The workflow can be structured and modified in a variety of ways. The following process is provided as a starting point but is not meant to be prescriptive.